#!/bin/python3

import sys

def sumOfGroup(k):
    startNum = 1
    stopping_point = (2*k) - 2
    increment = 0
    while increment <= stopping_point:
        startNum += increment
        increment += 2

    sum = 0

    for i in range(k):
        sum += startNum
        startNum += 2

    return sum

if __name__ == "__main__":
    k = int(input().strip())
    answer = sumOfGroup(k)
    print(answer)